Navy Aegis Ballistic Missile Defense (BMD) Program: Background and Issues for Congress [Updated April 25, 2019] [open pdf - 1MB]
From the Document: "This report provides background information and issues for Congress on the Aegis ballistic missile defense (BMD) program, which is carried out by the Missile Defense Agency (MDA) and the Navy, and gives Navy Aegis cruisers and destroyers a capability for conducting BMD operations. The issue for Congress is whether to approve, reject, or modify Department of Defense (DOD) acquisition strategies and proposed funding levels for the Aegis BMD program. Congress's decisions on the Aegis BMD program could significantly affect U.S. BMD capabilities and funding requirements, and the BMD-related industrial base."
CRS Report for Congress, RL33745
Congressional Research Service: https://crsreports.congress.gov/